Chlorine is universally used as a disinfectant for water at the critical level of 1-2 ppm. Field colorimetric methods for the measurement of this level chlorine are based on the chlorination of the organic chromophores DPD and orthotolidine. DPD is expensive, orthtolidine highly toxic; both are used by necessity rather than by choice.
A laboratory method for measuring chlorine level is the well known iodometric proceedure: potassium iodide reacted with chlorinated sample water to produce iodine, the iodine then measured by titration against a primary standard using disappearance of starch-iodine chromophore as the end point. Just combining starch and iodide solution as a colorimetric reagent without use of a back titrant has not worked. Combined aqueous starch/iodide solution is not stable, not sensitive enough to critical chlorine level, and over sensitive to interferents as a test reagent.
A stable, sensitive, interferent shielded iodometric test device for the measurement of chlorine in disinfectant water is the subject of my invention. An object of my invention is a method for making a safe and cheap test composition for colorimetric measurement of chlorine comprising starch/iodide reagent incorporated within a reducing fluid, the reducing fluid stabilizing said starch/iodide reagent, the fluid serving as a propellant to discharge such reagent in atomised form thereby improving such reagent in sensitivity, and the fluid serving as a shield against interferents by propelled entrainment within such discharge reagent. Another object of my invention is a method for packaging such composition within a valved enclosure, thereby making a suitable test device for chlorine measurement. Yet another object of my invention is a method for using said test device to colorimetrically measure chlorine concentration.